Densified carbonaceous bodies with improved surface finishes

ABSTRACT

A liquid impregnant containing furfural, an acid catalyst and a pore-forming agent comprising a surfactant, e.g. a polyalkylene oxide adduct, is impregnated into fine grained, isotropic graphite bodies and then polymerized and pyrolyzed. An increase in the density of the impregnated body and an improved surface finish is obtained by means of the liquid impregnant and method of this invention.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 689,842, filedJan. 9, 1985, which in turn is a continuation in part of U.S. patentapplication Ser. No. 568,066, filed on Jan. 4, 1984, which is adivisional of U.S. patent application Ser. No. 305,777, filed Sept. 25,1981, which issued on Jan. 10, 1984 as U.S. Pat. No. 4,425,316.

BACKGROUND OF THE INVENTION

In one aspect this invention relates to novel, improved techniques fordensifying and improving the surface finish of fine grained, isotropicgraphites.

The invention also relates, in a second aspect, to novel, improved,densified, carbonaceous artifacts which have a superior surface finishand are obtained by impregnating a fine grained, isotropic graphite witha liquid impregnant and subsequently first polymerizing and thenpyrolyzing or carbonizing the impregnant.

And, in two other aspects, this invention relates to novel, improvedliquid impregnants for use in the techniques of treating fine grained,isotropic graphites identified above and to the novel artifactsimpregnated therewith.

Fine grained, molded graphite parts have residual porosity whichdetracts from performance in some applications in which they are used,such as in crucibles and the like. For example, this porosity generallyadmits oxidizing media and allows the gaseous products of oxidation toleave the body, thereby generally lowering its oxidation resistance.

Also, in the case of certain crucibles for melting liquid metals, thesurface porosity allows some penetration of the liquid into the crucibleand thereby contributes to degradation of the crucible.

Also, graphite parts in contact with glass at high temperature aredegraded by glass entering the surface pores of the crucible. Thiscauses sticking and subsequent breaking away of the crucible surfacewhen the contact is broken. The pores also contribute to a general lossof strength.

In order to overcome these difficulties a wide variety of impregnationprocess have been practiced in the graphite industry.

For example, decomposition of a gas phase to close interconnected poresand prevent unwanted penetration of graphitic material is suggested inU.S. Pat. No. 3,084,394 to Bickerdike.

Impregnation of carbon and other porous bodies with furfural alcohol tofill their pores is described by I. S. Goldstein and W. A. Dreker inIndustrial Engineering Chemistry, 52, 57 (1960).

In U.S. Pat. No. 3,628,984, Ishikawa and Teranishi disclose the use of asolution of furfural and acetone with two catalytic additives toimpregnate graphite bodies in order to reduce porosity and improveproperties obtained after the body is cured in an acid bath andsubsequently carbonized. Unfortunately, both catalysts and the acetoneare required to achieve the desired results.

A group of liquids that can be cast into pyrolyzable, free-standingbodies, with highly controlled systems of porosity, is disclosed in U.S.Pat. No. 3,859,421. It has recently and unexpectedly been discoveredthat certain of these liquids can also be used to impregnatefine-grained, isotropic graphites. The subsequent polymerization andpyrolyzation of those liquid impregnants reduces the susceptibility ofthe impregnated graphitic body to degrative attack by increasing itsdensity and decreasing the average size of the number of interconnectedpores opening onto the surface of the body.

That fine grained, isotropic graphites can be successfully treated bythe technique just described is important because technical demands forhigher strength and quality, etc. and the elimination of anisotropiccharacteristics have led to the increasing use of such isotropicgraphites.

Fine grained graphites, such as those manufactured and sold by PocoGraphite Company, have grain sizes of about 0.001 inch and residual,interconnected pores typically about 0.4 micron in size. Thesefine-grained, small pore graphites yield a superior surface finish whenthey are machined.

However, it has been found that even these fine-pored graphites can beimpregnated, and surface finish and product performance furtherimproved, using the novel impregnating techniques and impregnantsdisclosed herein.

SUMMARY OF THE INVENTION

The present process for improving the properties of fine-grained,isotropic graphites involves the following steps:

(1) Preparing a liquid impregnant by mixing furfural or furfural alcoholor a mixture of those compounds and various pore forming agentscomprising a surfactant selected from the group consisting of anionic,cationic, nonionic and amphoteric surfactants, e.g. a polyalkylene oxideadduct at room temperature with an acid polymerization agent;

(2) Submersing the graphitic body to be impregnated in the liquidimpregnant;

(3) Polymerizing the liquid impregnant into a cured resin in the poresof the graphitic body by holding it at a desired temperature for anappropriate time; and

(4) Heating the graphite body, with the cured resin within it, to apyrolyzation temperature to convert the carbon in the cured resin toinorganic carbon.

Furthermore this invention provides a densified carbonaceous artifactwith a superior surface finish, said artifact comprising: a permeablebody composed essentially of a fine grained, isotropic graphite, thepores of said body being filled with the pyrolyzation product of a resinobtained by polymerizing an impregnant containing furfural, or furfuralalcohol or a mixture thereof, an acid catalyst, and a liquidpore-forming agent comprising a surfactant selected from the groupconsisting of anionic, cationic, nonionic and amphoteric surfactants apolyalkylene oxide adduct.

In addition, this invention provides a liquid impregnant for densifyinga permeable body composed essentially of a fine grained, isotropicgraphite, said impregnant comprising: furfural or furfural alcohol or amixture thereof, an acid catalyst, and one or more pore-forming agentscomprising a surfactant selected from the group consisting of anionic,cationic, nonionic and amphoteric surfactants e.g. a polyalkylene oxideadduct.

Finally, this invention provides a structure which is capable of beingconverted into a densified carbonaceous artifact, said structure beingcomposed of a body which is essentially a fine grained, isotropic carbonwith the pores thereof filled with a liquid impregnant containingfurfural and/or furfural alcohol, an acid polymerization catalyst, andone or more pore-forming agents comprising a surfactant selected fromthe group consisting of anionic, cationic, nonionic and amphotericsurfactants a polyalkylene oxide adduct or the polymerization productsof an impregnant as aforesaid.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, the impregnating liquids used are suited togive exceptional and unexpected results. Specifically, the prior artuses furfural alcohol, furfural alcohol resins, or furfural asimpregnants with the aim of producing a carbon within the pores of acarbon body in order to eliminate the pores within it. The materialstypically produce a carbon within the pores that is cracked due to thelarge shrinkage it undergoes upon carbonization or pyrolyzation.Exemplary of the processes that would be expected to produce carbonswith this susceptibility are those disclosed in the Bickerdike patentand the Goldstein article identified above.

Ishikawa et al. (see U.S. Pat. No. 3,628,904) were able to overcome thisdifficulty to some extent by using an impregnant composed of furfuralmixed with acetone and two catalysts.

However, upon pyrolyzation, the liquid impregnants of the presentinvention form a carbon in the pores of the impregnated body that haswithin it a much finer pore structure than any Ishikawa was able toproduce. This carbon has excellent strength and hardness.

The pores in the impregnant-based carbon, produced by the process of thepresent invention, are in the range of 100-1500 angstroms (0.01 to 0.15micron) and are interconnected, thereby allowing an escape route for thegases given off during carbonization. (Throughout this disclosure thedimension of the pores, referred to, is the diameter.) This structure isimportant as the cracking upon pyrolysis to which prior art impregnantswere susceptible is thereby avoided.

The liquid impregnants are also very low in viscosity and completely wetthe graphite allowing even the finest of the pores in the originalgraphite body to be filled with the impregnant. They furthermore undergomuch less linear shrinkage (18 to 22%) during carbonization than doespure furfural alcohol or furfural (35-45%). In addition no volatilecomponents such as acetone are present in said liquid impregnants. Thepresence of volatile compounds in the liquid impregnant is undesirableas such constituents tend to leave the body by evaporation, therebydrawing out the resin to the surface. This is undesirable both becauseit leaves an unwanted "skin" on the surface of the carbonaceous body andbecause pores in that body are left unfilled, thereby detracting fromthe very properties the impregnant is employed to provide.

One excellent liquid impregnant for the fine grained, isotropic graphitemanufactured by Poco Graphite Company can be made by dissolving paratoluene sulfonic acid (catalyst) in an ethylene oxide adduct ofoctylphenol, e.g. an ethyleneoxide adduct having about 40 moles ofethylene oxide and then adding furfural until the latter comprises fromabout 60 to about 80 volume % of the solution. The concentration of paratoluene sulfonic acid in this impregnant varies from about 5 to about 20weight % of the furfural.

Furfural alcohol may be substituted for furfural in whole or in part inthe foregoing mixture, and other polyalkylene adducts comprising ahydrophobic residue, e.g. polyethylene or polyethylene-polypropyleneadducts of alkylphenols, naphthol or alkylnaphthols may be substitutedin whole or in part for the above-exemplified adduct. Other acidcatalysts known in the art such as phosphoric and hydrocholoric acidsmay be used in place of the para toluene sulfonic acid. The exact ratiosof ingredients is not critical, and the concentration of each componentusually falls within the ranges specified below:

    ______________________________________                                        Acid Catalyst     2-20 weight % furfural/                                                       furfural alcohol                                            Furfural/         40-85 Volume %                                              Furfural Alcohol                                                              Pore-forming Agent                                                                              Balance                                                     ______________________________________                                    

The times and temperatures employed to first polymerize and thenpyrolyze the liquid impregnant can vary widely, depending upon thecomposition of the liquid impregnant. In general, the guidelines setforth in U.S. Pat. No. 3,859,421 for the consolidation and pyrolyzationsteps described therein can be followed; and the patent is, accordingly,incorporated herein by reference. In fact, even higher concentrations ofcatalyst are practically usable, allowing faster rates since theimpregnant is highly distended in a good conducting graphite body.

The pore-forming agent comprises a surfactant selected from the groupconsisting of anionic, cationic, nonionic and amphoteric surfactants.Examples of such surfactants include Soaps, Primary alkylammonium salts,Esters of polyhydric alcohols, Betaines, Sulfated esters, Secondaryalkylammonium salts, Alkoxylated amides, Amino Acids, Sulfated amides,Tertiary alkylammonium salts, Esters of polyoxyalkylene glycols,Sulfated alcohols, Quaternary alkylammonium salts, Ethers ofpolyoxyalkylene glycols, Sulfated ethers, Acylated polyamines,Alkylolamine-fatty Sulfated carboxylic acids, Salts of heterocyclicamines, Acid condensates, Petroleum sulfonates, Benzylammonium salts,Tertiary acetylenic glycols, Sulfonated aromatic hydrocarbons, Dialkylpolyoxyalkylene phosphates Sulfonated aliphatic hydrocarbons, Sulfonatedesters, Sulfonated amides, Sulfonated ethers, Acylated amino acids,Acylated polypeptides, Metal alkyl phosphates.

While not wishing to be bound by theory, it is believed that thefunction of the surfactant, in addition to its action as a pore-formingagent, is to uniformly disperse the solids generated during thepolymerization of the furfural or furfural alcohol monomers into thesolid resin. That is, as the solid phase begins to form, it is uniformlydispersed by the surfactant. By this action the pores resulting uponcarbonization of the solid resin are of a substantially uniformdimension and interconnecting.

Thus the surfactant functions as a dispersant for the solids formingfrom the polymerized liquid impregnant. In view of this theory, it willbe understood that increasing the concentration of the surfactant in theliquid impregnant will more finely disperse the solid resin therebyresulting, upon pyrolysis, in a composite having a smaller average poresize.

The surfactant must also volatilize during the subsequent pyrolysis ofthe furfural and/or furfural alcohol resin to form the microporousstructure. Thus, although the generally less volatile anionic, cationicand amphoteric surfactants are suitable pore-forming agents, thenonionic surfactants are preferred for their generally more desirablevolatility characteristics.

The pore-forming agent of the instant invention may be selected from thegroup consisting of compounds represented by the following generalformula I: ##STR1## wherein R¹ is a hydrophobic radical selected fromthe group consisting of hydrocarbyl and heteroatom substitutedhydrocarbyl radicals; R² and R³ are independently selected from thegroup consisting of hydrogen, hydrocarbyl and heteroatom substitutedhydrocarbyl radicals; x is an integer ranging from 1 to about 100 and yis an integer ranging from 1 to about 4. The heteroatoms that may besubstituted in the above hydrocarbyl radicals include halogen, oxygen,nitrogen, sulfur and phosphorus atoms. Preferably R¹ is derived fromcompounds selected from the group consisting of alkylphenols, naphthols,alkylnaphthols, carboxylic acids, amines, amides, phosphates andsulfates having at least 3 carbon atoms, more preferably at least 10carbon atoms, most preferably from about 14 to about 30 carbon atoms,e.g. about 15 carbon atoms, by reacting said compounds with an epoxide,e.g. ethylene oxide, propylene oxide, etc. R² is derived from theepoxide and is preferably selected from the group consisting of hydrogenand alkyl radicals having from 1 to 4 carbon atoms, more preferably R²is selected from the group consisting of hydrogen and methyl radicals,and most preferably R² is hydrogen. R² may be a mixture of radicals, forexample hydrogen and methyl when a mixture of ethylene oxide andpropylene oxide is reacted with the compound providing the hydrophobicradical. The mixture of ethylene oxide and propylene oxide may bereacted with the hydrophobic residue to provide block polymers or randompolymers. R³ is preferably selected from the group consisting ofhydrogen and alkyl radicals having from 1 to 4 carbon atoms; mostpreferably R³ is hydrogen. x preferably varies from about 10 to about60, more preferably from about 30 to about 50, e.g. about 40. y ispreferably 1 or 2; more preferably y is 1.

Examples of suitable pore-forming agents include the commerciallyavailable glycol ethers of alkyl phenols of the following generalformula II: ##STR2## wherein R⁴ is a substituted or unsubstituted alkylradical having from 1 to 18 carbon atoms, preferably 8 or 9 carbonatoms; a substituted or unsubstituted aryl radical or an amino group andn is an integer of from about 10 to about 100 preferably from about 30to about 50, e.g. about 40.

These nonionic surfactants are available in a wide array of molecularweights depending primarily on the value of "n", i.e. the number ofethylene oxide repeating units.

Procedures for the preparation of the glycol ethers of formula II arewell known and are described, for example, in U.S. Pat. Nos 2,213,477and 2,496,582, which disclosures are incorporated herein by reference.Generally, the production of these compositions involves the addition ofsubstituted phenols with varying molar proportions of ethylene oxidemonomer.

Preferably, said polyalkyleneoxide nonionic surfactants suitable for usein the invention include the glycol ethers of alkylated phenols of theabove general formula II: wherein R⁴ is an alkyl radical of from 1 to 18carbon atoms, preferably 8 or 9 carbon atoms; and n is an integer fromabout 10 to about 100, preferably from about 30 to about 50, e.g. about40.

The most preferred glycol ethers of the type generally described informula II are the octyl-or nonylphenoxy (polyethyleneoxy) ethanolcompositions of the formula wherein n ranges from about 30 to about 50.Commercially available surfactants of this type are supplied by the GAFCorporation under the designation IGEPAL. Other commercially availablesurfactants of this type are supplied by the Thompson-Hayward ChemicalCo. and Whitestone Chemical Co. These materials are also available fromRohm and Haas Corporation as TRITON surfactants, e.g. as Triton X-100.

Other suitable pore-forming agents are thepoly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) or, as otherwisedescribed, propoxylated, ethoxylated propylene glycol nonionicsurfactant block polymers of the general formula III:

    HO(CH.sub.2 CH.sub.2 O).sub.a [CH(CH.sub.3)CH.sub.2 O].sub.b (CH.sub.2 CH.sub.2 O).sub.c H

wherein a, b and c are positive integers and wherein a and c total fromabout 10 to about 100, e.g. from about 30 to about 50 and b ranges fromabout 5 to about 50. These surfactants comprise the block polymers ofethylene oxide and propylene oxide, with the repeating units ofpropylene oxide constituting the hydrophobic portion of the surfactantand the repeating units of ethylene oxide constituting the hydrophilicportion of the surfactant. These compositions can be prepared, and arecommercially available, in a variety of molecular weights, dependingprimarily on the number of repeating units of propylene and ethyleneoxide.

Suitable procedures for the production of the block polymers of FormulaIII are described in the patent literature in, for example, U.S. Pat.Nos. 2,674,619; 2,677,700 and 3,101,374, all three of which areincorporated herein by reference. Generally, these block polymers areprepared by a controlled addition of propylene oxide to the two hydroxylgroups of propylene glycol to form the hydrophobe, followed by thecontrolled addition of ethylene oxide to "sandwich" in the hydrophobebetween the two hydrophilic polyethyleneoxide groups. The nonionicsurfactants of this type (Formula III) are available from theBASF-Wyandotte Corporation under the PLURONIC designation.

Still other polyalkyleneoxide nonionic surfactants suitable for use inthe invention are the block polymers of ethylene and propylene oxidederived from nitrogen-containing compositions such as ethylene diamineof the general formula IV: ##STR3##

where R⁵ is an alkylene radical having from 2 to 5 carbon atoms,preferably 2; R⁶ is alkylene radical having 3 to 5 carbon atoms,preferably 3; d, e, f, g, h, i, j and k are positive integers; and h, i,j, and k total from about 10 to about 100 e.g. from about 30 to about50. d, e, f and g may total from about 4 to about 100, e.g. from about30 to about 60.

The polyalkylene oxide nonionic surfactants of formula IV are preparedby the addition of a C₃ to C₅ alkylene oxide to an alkylene diamineunder conditions to add two polyoxylakylene groups to each of thenitrogen groups in the presence of a catalyst so as to polymerize theoxyalkylene groups into the desired polyoxyalkylene radicals. After thedesired addition and polymerization of the C₃ to C₅ alkylene oxide grouphas been completed, ethylene oxide is introduced and is added to thepolyoxyalkylene groups to impart the desired hydrophilic characteristicsto the compound. The preparation of these materials from commerciallyavailable alkylene diamines and alkylene oxides is known in the art. Ingeneral, these surfactants are prepared by mixing the C₃ to C₅ alkyleneoxide with the alkylene diamine at atmospheric or elevated pressures, attemperatures between about 50° to 150° centigrade in the presence of analkaline catalyst such as an alkali metal hydroxide or alcoholate. Thedegree of polymerization or the size of the hydrophobic group iscontrolled by the relative proportions of C₃ to C₅ alkylene oxide andalkylene diamine, the alkylene oxide being introduced in sufficientquantity to obtain a hydrophobic base weight of about 200 to about 4000e.g. from 2000 to about 3600, although other weights can be provided.The surfactants of (formula IV) are available from the BASF WyandotteChemicals Corporation under the TETRONIC designation.

From the foregoing it will be apparent to the reader that one importantand primary object of the present invention resides in the provision ofnovel, improved, densified components and artifacts composed of finegrained, isotropic graphites which have a superior surface finish andare impregnated with inorganic carbon of yet finer, extremely smallgrained nature which is hard and strong and has interconnected pores andis highly resistant to cracking.

Another important, primary object of the invention resides in theprovision of methods for making components and artifacts of thecharacter identified in the preceding object.

Still another important, and primary, object of the invention is toprovide novel liquid impregnants for use in the process identified abovewhich are capable of wetting isotropic graphites, and consequentially,capable of filling even the finest pores of the structures into whichthey are impregnated.

And yet another important, and primary, object of the invention is toprovide novel impregnated structures which can be converted, by theapplication of heat, into components and artifacts of the characteridentified in the first of the foregoing objects with only minimalshrinkage of the materials with which the graphite structures areimpregnated.

Another more specific, but nevertheless important, object of theinvention resides in the provision of the methods in accord with thepreceding objects in which the artifact or component is made byimpregnating the fine grained, isotropic graphite with a liquidimpregnant containing furfural or furfural alcohol or a mixture thereof,an acid catalyst, and one or more of the above-described pore-formingagents; heating the impregnated structure until polymerization occurs;and then pyrolyzing the organic constituents of the impregnant toproduce a still finer grained carbon in the pores of the isotropicgraphite.

A related, still more specific, object of the present invention residesin the provision of methods in accord with the the preceding object inwhich the impregnant contains furfural or furfural alcohol or a mixturethereof, para toluene sulfonic acid, and octylphenoxy-(polyoxyethylene)ethanol having about 40 moles of ethylene oxide.

Still other specific objects of the present invention reside in theprovision of impregnants of the composition identified in the twopreceding objects; in the provision of fine grained, isotropicstructures impregnated with such compositions and their polymerizationproducts; and in the provision of components and artifacts obtained bypyrolyzing the organic constituents of the impregnant.

Other important objects, features and advantages of this invention willbecome apparent to the reader from the foregoing, from the appendedclaims, and from the following examples which are intended only toillustrate, and not restrict, the scope of the invention as defined inthe appended claims.

EXAMPLES

In the Examples below a polyethylene oxide adduct of octyl phenol (i.e.an octylphenoxy(polyethyleneoxy)ethanol) having 40 moles of ethyleneoxide is compared to various glycols as a pore-forming agent forcarbon-producing liquid impregnants and to a liquid impregnant notincluding a pore-forming agent. The porosity of the resulting graphitecomposition is measured by determining its permeability to helium atvarious pressures. The polyethyleneoxide adduct is TRITON X-100 fromRohm & Haas Co.

Regardless of the impregnant formulation used, all impregnations arecarried out under the same process steps. The evacuation,pressurization, curing and baking cycle are all held constant. Allhelium flow rates are given in cc/minute and are obtained from quarterinch thick samples. All weight pickups are calculated after the finalbake.

EXAMPLE I--Polyethylene oxide Adduct as the Pore Forming Agent

    ______________________________________                                        Components             A (%)  B (%)                                           ______________________________________                                        Furfural              73.8    52.9                                            Furfural Alcohol      --      9.5                                             Polyethylene oxide Adduct                                                                           17.2    31.4                                            p-Toluenesulfonic Acid (pTSA)                                                                        9.0    6.2                                             Percent Weight Pickup  3.21    3.03                                           ______________________________________                                               cc He/Minute at the given p.s.i.g.                                     Impregnant                                                                              40    60      80  100    120  140    160                            ______________________________________                                        A        0.0   0.3     1.0 1.5    2.2  2.9    3.9                             B        0.0   0.0     0.3 0.5    0.9  1.4    2.1                             ______________________________________                                    

EXAMPLE II--No Pore Forming Agent

Composition: 91.7% Furfural and 8.3% pTSA

Percent Weight Pickup=3.02%

No helium flow detected up to 160 p.s.i.g.

EXAMPLE III--Glycols as Pore Forming Agents

    ______________________________________                                        Components      A (%)  B (%)    C (%) D (%)                                   ______________________________________                                        Furfural       54.8    64.6     74.6  54.6                                    Monoethylene Glycol                                                                          36.8    0.0      0.0   0.0                                     Triethylene Glycol                                                                           0.0     27.0     17.0  0.0                                     Tetraethylene Glycol                                                                         0.0     0.0      0.0   37.1                                    p-Toluenesulfonic Acid                                                                       8.4     8.4      8.4   8.3                                     Percent Weight Pickup                                                                         2.28    3.39     3.71  2.43                                   ______________________________________                                               cc He/Minute at the given p.s.i.g.                                     Impregnant                                                                              40    60      80  100    120  140    160                            ______________________________________                                        A        0     0       0   0      0    0      0                               B        0     0       0   0      0    0      0                               C        0     0       0   0      0    0      0                               D        0     0       0.1 0.4    1.0  1.7    2.3                             ______________________________________                                    

Example IIIC is similar to Example IA in that both comprise about 75percent furfural and about 17 percent of the pore-forming agent (byweight). Note however that the pore-forming agent of the presentinvention is permeable to helium at a pressure of as low as 60 psigwhile at a pressure of 160 psig Example IIIC is impermeable. Thiscomparison demonstrates that the pore-forming agents of this inventionprovide interconnected micropores in the carbonized or pyrolyzedcomposites.

Example IIID shows some permeability to helium at the pressures tested;however, the impregnant comprises 37 percent, by weight, of the glycol.A comparison of Example IA and IIIC demonstrates that a porous compositemay be obtained, with the liquid impregnants of this invention, at amuch lower concentration of pore-forming agent than with liquidimpregnants comprising glycols.

The porosity characteristics and surface areas of certain of thegraphite compositions are tested by means of mercury porosimetry and theresults summarized below:

    ______________________________________                                                     Example                                                                      IA   IB         II     IIID                                       ______________________________________                                        Average Pore  0.13   0.04       0.08 0.15                                     Size, Microns                                                                 Percent Closed                                                                              41     34         50   27                                       Porosity                                                                      Surface Area, 2.3    6.3        2.3  2.3                                      m.sup.2 /gm                                                                   ______________________________________                                    

A comparison of EXAMPLES IA and IB shows that a higher concentration ofthe surfactant decreases the average pore size. Moreover, a comparisonof EXAMPLES IB and IIID, demonstrates that, at substantially equivalentconcentrations of a glycol and a surfactant, the surfactant provides adecreased pore size.

Note also that, when a pore-forming agent is omitted, the resultinggraphite composition has 50 percent closed pores, while less than 50percent of the pores are closed when a pore-forming agent is used.Moreover, when the pore-forming agent of this invention is compared tothe glycol pore-forming agent, a smaller average pore size is obtainedwith approximately equivalent open porosity. (Compare, e.g. EXAMPLES IBand IIID.)

Representative forms of the present invention have been described above,but the invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thedisclosed embodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription; and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. A structure which is capable of being convertedinto a densified carbonaceous artifact, said structure being composed ofa body which is essentially a fine grained, isotropic carbon with thepores thereof filled with a liquid impregnant containing furfural and/orfurfural alcohol, an acid polymerization catalyst, and one or morepore-forming agents comprising a polyalkylene oxide adduct or thepolymerization products of an impregnant as aforesaid.
 2. A structure asdefined in claim 1 and capable of being converted into a densifiedcarbonaceous body wherein the constituents of the impregnant are presentin the following properties:

    ______________________________________                                        Furfural, furfural alcohol                                                                        40-85 Volume %, and                                       or mixture thereof                                                            Acid catalyst       2-20 Weight % based                                                           on furfural, furfur-                                                          al alcohol or mix-                                                            ture thereof.                                             ______________________________________                                    


3. A structure as defined in either of the preceding claims 1 or 2 andcapable of being converted into a densified carbonaceous body whereinthe acid catalyst constituent of the impregnant is para toluenesulfonic, phosphoric, or hydrocholoric acid.
 4. A structure as definedin either of the preceding claims 1 or 2 and capable of being convertedinto a densified carbonaceous body wherein the pore-forming agentconstituent of the impregnant comprises a polyethylene oxide adduct. 5.A structure as defined in claim 4 and capable of being converted into adensified carbonaceous body wherein the pore-forming agent constituentof the liquid impregnant comprises a polyethylene oxide adduct of analkylphenol.
 6. A structure which is capable of being converted into adensified carbonaceous artifact, said structure being composed of a bodywhich is essentially a fine grained, isotropic carbon with the poresthereof filled with a liquid impregnant containing furfural and/orfurfural alcohol, an acid polymerization catalyst, and one or morepore-forming agents comprising a surfactant selected from the groupconsisting of anionic, cationic, nonionic and amphoteric surfactants orthe polymerization products of an impregnant as aforesaid.